Hybrid transformer coupling network for very high frequencies



Jan. 1, 1952 D. WEIGHTON 2,581,156 HYBRID TRANSFORMER COUPLING NETWORK FOR VERY HIGH FREQUENCIES Filed Jan. 27, 1948 g g I Inventor -D "nald Heighi'on Attorneys Patented Jan. 1, 1952 HYBRID TRANSFORMER COUPLING NET- WORK FOR VERY HIGH FREQUENCIES Donald Weighton,

to Pye Limited, company Application January 27 In Great Britain 3 Claims.

In radio transmitters for aircraft blind approach and landing systems, it is sometimes necessary to provide means for combining the outputs of two phased transmitters to feed the elements of a common aerial system in such a manner that the outputs are combined in phase in some aerials and in antiphase in other aerials. The present invention provides a hybrid transformer for use at very high frequencies, which is particularly suitable for so combining the outputs of two transmitters, although it is applicable to other uses.

The invention will be described with reference to the Figures 1 and 2 of the accompanying drawing which show respectively an elevation and plan of a preferred form of the transformer. The transformer consists of a section of a balanced transmission line in which at least one of the members I and 2 is a hollow metal conductor. The members I and 2 are connected together at one end, preferably by a screen 3 which may enclose the whole apparatus, and a concentric transmission line 4 is led up the hollow member 2 which may form its outer conductor. The central conductor 4 of this concentric line is connected at the open end to the Cambridge, England, assignor Cambridge, England, a British 1948, Serial No. 4,653 January 28, 1947 opposite member I of the balanced pair. The

inner conductor 5a of a furthenconcentric line 5 is connected to the centre of a conducting bridge 8 connected across the balanced pair at apoint which is not at a multiple of a half wavelength from either end of the pair, and the outer conductor 5b is connected to the short circuited ends of the transmission line, preferably by the screen 8. Connections are made from the unbalanced transmission lines 8 and 1 to the open ends of the balanced pair, care being taken to ensure that the various elements external to the hollow transmission lines are disposed symmetrically with respect to their median plane.

The transformer may be used either by connecting the two transmitters to the lines 6 and 1 when they are combined at the output 5 in phase and at the output 4 in antiphase, or by connecting the two transmitters to the lines 4 and 5 when they are combined at the output 8 in phase and the output I in antiphase.

The manner of operation of the transformer is as follows. When signals for the two phased transmitters are applied respectively to the transmission lines 6 and 1 they will arrive in phase at the conductor 5a, which is connected at the centre of the bridge 8, since the distances along the members I and 2 between the transmission lines 6 and 1 and the point 5a are equal. As previously mentioned, the bridge 8 is connected across the members I and 2 at a point which is not a multiple of a half wave length from either end of the members and therefore the portion of members I and 2, between the bridge 8 and the screen 3, constitutes a reactance connected .across the concentric line 5 and therefore does not interfere with the operation of the device. If a load is connected to the line I, it will in effect, be connected across the lines 6 and 'l, by reason of the concentric line comprising the hollow member 2 and the central conductor 4, and the signal applied to the load will therefore be the difference between the signals applied to the lines 6 and 1, that is, these signals will appear across the load in opposite phase. Since the length between the open end of the balanced members I and 2, and the bridge 8, is not a multiple of a half wave length, the circuit comprising members land 2 and the bridge 8 comprises a reactance connected across the lines 6 and I, and will therefore not interfere with the operation of the device.

I claim:

1. Hybrid transformer for use at very high frequencies, comprising a pair of members forming a section of a balanced transmission line of which at least one of the balanced pair of members is a hollow metal conductor, means connecting the two members at one end, a central conductor arranged in the hollow member to form with the latter a concentric transmission line, said central conductor being connected at the open end of the concentric line to the other member of the balanced pair, and a further concentric line of which the inner conductor is connected to the centre of a conducting bridge connected across the balanced pair at points along the length thereof, the outer conductor of this further concentric'line being connected to the short-circuited ends of the pair of members.

2. Transformer as claimed in claim 1, wherein the open ends of the balanced pair are connected to a pair of unbalanced transmission lines.

3. Transformer as claimed in claim 2, wherein the conductor connecting the short-circuited ends of the balanced pair comprises a metal screen which encloses the whole apparatus.

' DONALD .WEIGHTON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,222,169 Buschbeck et al. Nov. 19, 1940 2,327,418 Goldman Aug. 24, 1948 

